The three levels model based on J2EE platform is introduced, of which more emphasis on design and realization of the navigating engine is given.

介绍了基于J2EE平台的三层模型设计，并注重研究了导航引擎的设计与实现。

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Casio has redesigned the ClassPad series' software keyboard to make this new model easier to use, organizing functions to correspond to three levels of learning difficulty, beginning with basic functions used by everyone like fractions, square roots, and trigonometric functions, then advanced functions like differential calculus, complex compound numbers, and sigma calculations, and finally even more advanced calculations including piecewise and user-defined formulas.

ENGADGET: Casio's touchscreen graphing calculator arrives in 2013, makes the TI-84+ look dated

But the computer model suggested Ford would do better if it offered three models, with different equipment levels.

FORBES: How computers tell Ford when to put on a rebate.